Pusher-type centrifuge



June 9, 1964 F. P. GOOCH 3,136,722

PUSHER-TYPE CENTRIFUGE Filed Oct. 18, 1961 3 Sheets-Sheet 1 IN VENTOR.

FRED P. GOOCH ATTORNEY June 9, 1964 p, GQQCH 3,136,722

PUSHER-TYPE CENTRIFUGE Filed Oct. 18, 1961 3 Sheets-Sheet 2 INVENTOR.

FRED P. GOOGH MAM 4W ATTORNEY June 9, 1964 p, GOOCH 3,136,722

PUSHER-TYPE CENTRIFUGE Filed Oct. 18, 1961 3 Sheets-Sheet 5 INVENTOR FRED P. GOOCH ATTORNEY United States Patent 3,136,722 PUSHER-TYPE CENTRIFUGE Fred P. Gooeh, Moline, 111., assignor to Pennsalt Chemicals Corporation, a corporation of Pennsylvania Filed Oct. 18, 1961, Ser. No. 145,811

Claims... (Cl. 210-376) This invention relates to the separation of solids from a liquid by centrifugal force. More specifically this invention relates to a continuous dehydrator of the pusher type comprising a perforate ,rotor enclosing a rotating reciprocable pusher member which, in reciprocating, advances solids axially along the perforate rotor toward discharge.

An example of an apparatus of the general nature of that of the present invention is disclosed in the US. Patent 1,842,464 which issued January 26, 1932 to Ter Meer. The prior art has recognized the advantages to be gainedin constructing the pusher'member of gentle frusto-conical shape and providing it with a perforate draining surface to which the feed is delivered. By such construction of the pusher member, or inner rotor as it may be regarded, a great deal of liquid is thrown off of the solids without the need for the power necessary to accelerate the liquid at the radius of the outer rotor. Additionally, by facing the perforate inner rotor toward the discharge end of theouter rotor, the liquid thrown off while the solids are on the inner rotor is thrown directly outward without need for diverting channels or passages to avoid recontact of the liquid with the partially dehydrated solids on the outer rotor. Drainage is hence more elfective. I

While the devices of the prior art have to some extent accomplished their desired purpose, namely the dehydra tion of solids using reduced power by virtue of the inclined draining surface they have fallen short in at least one respect. In order to provide compactness for purposes of conserving plant floor space, and more importantly, to keep to a minimum the length of the rotating inner rotor to reduce inertial problems and power requirements, the inclined draining surface has been made too abrupt to be effective. Alternatively, the feed mixture has been introduced directly to the inner rotor at a distance greatly spaced from the axis ofthe rotor causing rapid acceleration and shear to the extent that there has been, for instance, crystal breakage.

Crystal breakage is undesirable because it results in reduction of crystal size'to permit passage of more crystal material through the openings in the outer rotor with the liquid discharge. In addition, the operator who may have taken great pains to growcrystals,to a desired-size before centrifuging wishes to maintain the crystals at that size if at all possible. Often their size will determine crystal properties. For instance, it is recognized that large crystals flow and fall-with greater uniformity. and ease than smaller crystals, and that large crystals tablet (forjinstanc'e, in the making of aspirin) better than small crystals. Additionally, large crystals having less surfaceexposure per unit weight will dissolve at a slower rate than small crystals, and therefore ammonium sulphate crystals used as fertilizer will dif fuse into the' soil at a slower rate if crystals'are large. Finally, and most importantly, large crystals because they are believed,,ri ghtly or wrongly, to be more pure, have greater sales appeal thanismall crystals. i By the apparatus embodying my invention I have eliminatedlth drawback of the prior. devices, retaining their advantages. More specifically, by gradually accelerating the feed mixture toward the drain surface of the inner rotor, Ihave considerably reduced solids breakage while not increasing the power demands appreciably to rotate the inner rotor. Moreover, by my invention desired results are obtained without sacrificing the compactness which was an attribute of the prior art devices.

This invention embodies other novel features, details of construction and arrangement of parts which are hereinafter set forth in the specification and claims, and illustrated in the accompanying drawings, wherein:

FIGURE 1 is a top plan view of an apparatus embodying the invention; 7

FIGURE 2 is an enlarged elevational view partly in section taken on the line 2-2 of FIGURE 1;

FIGURE 3 is an elevational view partly in section taken on the line 3-3 of FIGURE 1; and

FIGURE 4 is a sectional view taken on the line 4-4 of FEGURE 2 and showing portions of the structure peeled away to illustrate the relation of parts beyon the plane 44 of FIGURE 2.

Briefly, in a centrifugal continuous solids drier of the pusher type having an outer perforate rotor and an inner frusto-conical perforate rotorfacing the discharge end of the outer rotor, the invention involves the provision of an imperforate distributing shell circurnposing an axial feed tube and adapted to gently accelerate the feed mixture to the perforate frusto-conical inner rotor.

Acceleration as used herein, unless otherwise indicated may be taken to mean tangential acceleration.

Referring more specifically to the drawings, an apparatus embodying the invention is shown in FIGURE 1 and generally designated 19. its rotating elements may be driven by a suitable motor M which is conveniently of a conventional type. The apparatus 1i} com prises a base or frame member 12 adapted to be secured as by bolts to a suitable support surface. intermediate its ends the frame 12 mounts upstanding brackets 14 which by means of-resilient spacers 14a (FIG. 3) horizontally support the shaft housing 16. Preferably the spacers Ma are radially disposed peripherally spaced blocks. Concentrically secured within the shaft housing 161 are a plurality of aligned ball-bearing units 18 (FIG. 3) to the center races of which is aflixed the tubular outer rotor drive shaft 20. The bearin units are spaced by tubular spacer 19. As shown in FIG. 1 a multiple belt drive from motor M engages a multiple pulley 22 mounted on the rightward end of the tubular drive shaft 20, whereby the shaft Zti is driven at the appropriate speed.

FIGURE 2 represents that in a zone adjacent its letward end shaft 20 is tapered and receives the correspondingly central opening of the outer rotor 24. The extreme end of the shaft Zll is threaded and receives a securing nut 26, assuring co-rotation of shaft 20 and rotor 24. The rotor 24 includes a frusto-conicalportion plications a bar' screen. 38 is secured across the inner fa'ceof the basket, such screen comprising bars extending in axial direction and being held in position byrmeans well known in the art. To simplify the drawings the bar screen 38 is shown only partially iii-FIGURE 2.

Mounted for coaxial rotation with the' tubularshaft.

2tl'isthe inner rotor drive'shaft For convenience the shafts 20 and 40 may be linked for 'co-rot ation by a .key

42 in the shaft 20 which engages in a groove inthe inner shaft 40. Alternatively, the frictional engagement of is formed with a tapered zone and receives the hub element 46 of the inner rotor. The nut 47 holds the hub element to shaft 40. The radial vanes 48 are secured to the end of the nut. The hub element 46 is frusto-conical in shape as shown in FIGURE 2 and inclines toward the right as its outer perimeter is approached. Adjacent its perimeter the hub element mounts the frusto-conical perforate section 50 which comprises the inner rotor proper. In a manner similar to the basket 32 section 50 is formed with uniformly spaced annular grooves 52 and communicating openings 54. The outer periphery of the section 50 carries on its radial face an annular push element 56 which is positioned adjacent the screen 38.

As indicated in FIGURE 3 the opening through the hollow shaft is provided intermediate its ends with a reduced bushing 58 against which abuts one end of an axial spring 60, disposed about the shaft 40. Adjacent its rightward end the shaft 48 is threaded and engaged by a nut 62 supporting a flanged collar 64 against which the opposite end of spring 60 abuts. There is an urging, therefore, by spring 60 to return the inner rotor including push element 56 to the retracted position. Supplying the force to drive the section 50 toward the open end of the outer rotor 32 is the piston 66 secured axially to the extreme end of shaft and operable in the cylinder 68. The piston 66 is activated by fluid communicating with the cylinder 68 through the fitting 70, conveniently of conventional design.

To provide for lubrication of the bearings 18, spaced heads 72 mounted in the housing 16 are adapted to direct oil at the bearings, respectively. Used oil will drain out fitting 74 for subsequent recirculation. For simplicity, lubrication lines are not shown in the drawings.

Surrounding the outer rotor 32 and anchored to the frame 12 is the cylindrical cover element 76. At its rightward end the cover element 76 is formed with an enlarged boss featuring a seal 78 adapted to engage leftward extensions of the shaft housing 16. Adjacent its opposite end, cover 76 is provided with an annular flange element 80 cooperating with an axially disposed fin 82 on basket 32 to provide an interlocking seal precluding recombination of extracted liquid within the cover with the solids discharge.

As shown in FIGURE 2 the cover may be formed with a plurality of inward annular partitions 84 compartmenting the cover into the desired number of drain zones. As illustrated each drain zone is provided with a drain outlet 85. Flush tubes 86 are also provided for cleaning out the drain zones if necessary. The zone 87 receives the solids discharge.

The leftward end of the cover 76 mounts an axial packing gland 88 of conventional design which receives in liquid-tight fit the feed tube 90 through which the feed slurry or the like, is introduced into the machine. The leftward end of the feed tube 90 is attached to a flexible pipe (not shown) to permit movement of tube 90.

The outlet end of tube 90 is reduced and threaded exteriorly and receives a correspondingly threaded discharge flange 92 which gently fans outward and is threadedly adjustable toward and away from radial vanes 48 secured to the nut 47. The distal end of the flange 92 may be in substantially the same plane as push element 56 to give the unit maximum compactness.

FIGURE 2 indicates that in its preferred form the outlet from feed tube 90 is closely circumposed by a feed distribution shell broadly designated 94. The shell 94 includes a collar 96 to which is bolted a pair of annular plates 98, 99 shaped to hold clampingly the outer race of a ball-bearing unit 100 circumposed by shock element 101. As FIGURE 2 indicates, the inner race snugly engages about feed tube 90, and the plates 98, 99 each carry appropriate seals 102 to preclude axial seepage of feed along the outside of the tube 90.

Adjacent its rightward end collar 96 has secured a ring 104 to which may be welded the smaller end of an axially disposed frusto-conical flaring distributor 106, along which solids introduced to the apparatus are gently accelerated as they move outward. The acceleration means comprise the vanes 108 secured to the hub element 46 as by welding and at their opposite end to a ring 110 which is bolted to the collar 96 as shown.

Thus by virtue of the present structure, the vanes 108 as well as the flaring distributor 106 reciprocate and rotate with the inner rotor 50. It will be noted that slurry passing through the outlet of the feed tube 90 by means of flange 92 is deposited on the inner face of collar 96 and thence moves outwardly along the flaring distributor 106 being gradually accelerated by the vanes 108. From the larger end of the distributor 106, the feed is deposited on the perforate frusto-conical section 50 and is immediately denuded of a large portion of its liquid as its movement from the axis of the apparatus along section 50 continues. The extracted liquid passes out openings 54 and 30 to be thrown directly out in the cover 76.

Additional Wings 112 secured to and extending radially outward from the distributor 106 assure the continued tangential acceleration of the feed.

Cake levelers 113 and 113a are secured to ring 104 as shown.

The feed, partially deliquefied, is hence delivered over push element 56 to the inner end of the perforate basket 32. As with pusher type apparatuses of the prior art, cake builds up in annular layer on the basket 32 and is urged leftwardly with each reciprocation, that is each leftward movement of section 50. Upon each leftward movement dry solids discharge is thrown over the outer end of the basket 32 for appropriate collection at zone 87. The succeeding abrupt rightward movement of the section 50 including push element 56 leaves adjacent element 56 an open area on basket 32 which is immediately filled by solids moving outward along section 50.

To assure evenness of feed to the apparatus it has been found desirable to maintain even spacing between flange 92 and nut 47. This, of course, has required the reciprocation of the feed tube 90. In the apparatus embodying the present invention this has been effectively accomplished by forming the feed tube 90 with a pair of spaced grooves (FIGURE 2) into which are received a pair of snap rings 114. The snap rings 114 in protruding radially outward from tube 90 provide shoulders for the inner race of bearing unit 100, forcing co-reciprocation of the tube 90 with the unit 100.

As has been achieved in the prior art, rinsing of the partially dried solids may be effected by one or more washing heads 116 which are supported on pipes held in appropriate bushings 118 in the leftward end of the apparatus as shown in FIGURE 2. The pipes may be adjusted in the bushings 118 and may be reciprocated with the feed tube 90 by suitable brackets, if desired. Preferably, as shown, a plurality of heads 116 are used and each are arranged to direct rinse toward the basket over the respective drain zones 85 for reasons well known in the art.

To observe action of the solids in the machine, a window 120 may be provided in the cover 76. Windows 121 and 121a may also be provided across openings in the cake levellers 113 and 113a.

In using feed mixture such as a slurry of ammonium sulfate crystals in the mother liquor, it is found that the crystals discharging in deliquefied form from the present apparatus are of substantially the same size as those in the feed and that there is a minimum loss of crystal material to the liquid discharge. Hence it is assumed that the frusto-conical distributor 106 coupled with the vanes 108 assure the gradual acceleration of the crystals to the tangential velocity of section 50 at its inner periphery, such gradual acceleration eliminating the shear and the other disturbances which cause crystal breakage.

The use of the apparatus in processing ammonium sulfate crystals is merely illustrative. The device is useful in deliquefying many solids. It is useful in, for instance, the removal of ice from water or other liquids, the separation of table salt from water, and the removal of polyvinyl chloride from its mother liquor.

It is therefore to be understood that the above particular description is by way of illustration and not of limitation, and that changes, omissions, additions, substitutions and/or other modifications may be made without departing from the spirit of the invention. Accordingly it is intended that the patent shall cover, by suitable expression in the claims, the various features of patentable novelty that reside in the invention.

I claim:

1. A compact centrifugal continuous solids drier of the pusher type comprising in combination an outer cylindrical rotor having a liquid-draining surface composed of smooth spaced bars disposed longitudinally thereof and an inner rotor coaxial within the outer rotor and defined by a central portion and an outer frusto-conical perforate portion, the larger end of the frusto-conical portion comprising an annular push surface and facing an open end of the outer rotor, means for rotating the rotors together, means for reciprocating the inner rotor relative to the outer rotor, a feed tube extending axially into the said open end of the outer rotor and terminating in an outlet, the margin of the outlet being flared and spaced from the central portion of the inner rotor, an imperforate flaring distributor shell mounted for rotation with the inner rotor, the smaller end of the shell closely circumposing the flared outlet of the feed tube, the larger end of the shell disposed'adjacent the inner periphery of the outer frusto-conical portion of the inner rotor, and vane means positioned radially and extending between the frusto-conical portion and the shell, and the shell and the central portion, respectively, to assure that the solids maintain the angular velocity of the respective elements as they traverse them, whereby solid material in a slurry introduced through the feed tube is gently accelerated by the shell to the frusto-conical portion, is progressively drained on the frusto-conical portion as acceleration gently continues, and is deposited at each reciprocation in annular cake form on the outer rotor for additional draining and subsequent discharge, the smooth bars of the cylindrical outer rotor presenting draining surface with minimum likelihood of solids abrasion.

2. A centrifugal continuous solids drier as described in claim 1 wherein the flaring distributor shell is mounted on the inner rotor and the smaller end of the shell is rotatably secured about the feed tube and means are provided to lock the shell for axial movement with the feed tube, whereby the feed tube reciprocates with the inner rotor.

3. A centrifugal continuous solids drier as described in claim 1 wherein the means for reciprocating the inner rotor relative to the outer rotor comprises spring means to retract abruptly the inner rotor and fluid pressure motor means to drive the inner rotor out.

4. A centrifugal continuous solids drier as described in claim 1 wherein an annular cake-leveling dam is mounted to reciprocate with the inner rotor and disposed toward the open end of the cylindrical rotor from said annular push surface.

5. A centrifugal continuous solids drier as described in claim 1 wherein additional vane means are radially disposed and mounted on the central portion adjacent the axis thereof and extend into the flared margin of the outlet of the feed tube.

References Cited in the file of this patent UNITED STATES PATENTS 1,842,464 Ter Meer Jan. 26, 1932 2,367,961 Piponius Jan. 23, 1945 2,685,370 Ruegg Aug. 3, 1954 2,755,934 Ruegg July 24, 1956 2,806,603 Van Der Molen Sept. 17, 1957 2,828,021 Ruegg Mar. 25, 1958 3,087,621 Gooch Apr. 30, 1963 3,123,557 McPhee et al. Mar. 3, 1964 FOREIGN PATENTS 590,969 Great Britain Aug. 1, 1947 750,531 Great Britain June 20, 1956 1,024,145 France Ian. 7, 1953 1,079,551 Germany Apr. 7, 1960 

1. A COMPACT CENTRIFUGAL CONTINUOUS SOLIDS RIDER OF THE PUSHER TYPE COMPRISING IN COMBINATION AN OUTER CYLINDRICAL ROTOR HAVING A LIQUID-DRAINING SURFACE COMPOSED OF SMOOTH SPACED BARS DISPOSED LONITUDINALLY THEREOF AND AN INNER ROTOR COAXIAL WITHIN THE OUTER ROTOR AND DEFINED BY A CENTRAL PORTION AND AN OUTER FRUSTO-CONICAL PERFORATE PORTION, THE LARGER END OF THE FRUSTO-CONICAL PORTION COMPRISING AN ANNULAR PUSH SURFACE AND FACING AN OPEN END OF THE OUTER ROTOR, MEANS FOR ROTATINGTHE ROTORS TOGETHER, MEANS FOR RECIPROCATING THE INNER ROTOR RELATIVE TO THE OUTER ROTOR, A FEED TUBE EXTENDING AXIALLY INTO THE SAID OPEN END OF THE OUTER ROTOR AND TERMINATING IN AN OUTLET, THE MARGIN OF THE OUTLET BEING FLARED AND SPACED FROM THE CENTRAL PORTION OF THE INNER ROTOR, AN IMPRFORATE FLARING DISTRIBUTOR SHELL MOUNTED FOR ROTATION WITH THE INNER ROTOR, THE SMALLER END OF THE SHELL CLOSELY CIRCUMPOSING THE FLARED OUTLET OF THE FEED TUBE, THE LARGER END OF THE SHELL DISPOSED ADJACENT THE INNER PERIPHERY OF THE OUTER FRUSTO-CONICAL PORTION OF THE INNER ROTOR, AND VANE MEANS POSITIONED RADIALLY AND EXTENDING BETWEEN THE FRUSTO-CONICAL PORTION AND THE SHELL, AND THE SHELL 